Does the optimization of cardiac output by fluid loading increase splanchnic blood flow?

We studied the effects of increasing cardiac output by fluid loading on spl anchnic blood flow in patients with haemodynamically stabilized septic shoc k. Eight patients (five female, 39-86 yr) were assessed using a transpulmon ary thermo-dye-dilution technique for the measurement of cardiac index (CI) intrathoracic blood volume (ITBV) as a marker of cardiac preload and total blood volume (TBV). Splanchnic blood flow was measured by the steady state indocyaninegreen technique using a hepatic venous catheter. Gastric mucosa l blood flow was estimated by regional carbon dioxide tension (PRCO2) Hydro xyethyl starch was infused to increase cardiac output while mean arterial p ressure was kept constant. In parallel, mean norepinephrine dosage could be reduced from 0.59 to 0.33 mug kg(-1) min(-1). Mean (SD) TBV index increase d from 2549 (365) to 3125 (447) ml m(-2), as did ITBV index from 888 (167) to 1075 (266) ml m(-2) and Cl from 3.6 (1.0) to 4.6 (1.0) litre min(-1) m(- 2). Despite marked individual differences, splanchnic blood flow did not ch ange significantly neither absolutely (from 1.09 (0.96) to 1.19 (0.91) litr e min(-1) m(-2)) nor fractionally as part of Cl (from 28.4 (19.5) to 24.3 ( 16.3)%). Gastric mucosal PRCO2, increased from 7.7 (2.6) to 8.3 (3.1) kPa. The PCO2-gap, the difference between regional and end-tidal PCO2, increased slightly from 3.2 (2.7) to 3.4 (3.1) kPa. Thus, an increase in cardiac out put as a result of fluid loading is not necessarily associated with an incr ease in splanchnic blood flow in patients with stabilized septic shock.